Electrochemical cells, or batteries, are commonly used as electrical energy sources. A battery contains a negative electrode, typically called the anode, and a positive electrode, typically called the cathode. The anode contains an electrochemically active anode material that can be oxidized. The cathode contains an electrochemically active cathode material that can be reduced. The electrochemically active anode material is capable of reducing the electrochemically active cathode material. A separator is disposed between the anode and the cathode. The battery components are disposed in a can, or housing, that is typically made from metal.
When a battery is used as an electrical energy source in an electronic device, electrical contact is made to the anode and the cathode, thereby completing a circuit that allows electrons to flow through the device, and which results in respective oxidation and reduction reactions that produce electrical power to the electronic device. An electrolyte is in contact with the anode, the cathode, and the separator. The electrolyte contains ions that flow through the separator between the anode and cathode to maintain charge balance throughout the battery during discharge.
There is a growing need for portable power for electronic devices such as toys; remote controls; audio devices; flashlights; digital cameras and peripheral photography equipment; electronic games; toothbrushes; radios; clocks, and other portable electronic devices. Consumers need to have power readily available for these electronic devices. Because batteries necessarily become depleted of power over time as they are used, consumers need to have access to spare batteries (and/or access to fully recharged rechargeable batteries). It is helpful for a consumer to know the power state of a battery currently in use so that the consumer can have quick access to the needed number of replacement batteries. Batteries come in common sizes, such as the AA, AAA, AAAA, C, and D battery sizes, that have fixed external dimensions and constrained internal volumes per ANSI standard.
Currently, some batteries include on-cell battery charge indicators to help a consumer determine when a battery is nearly depleted and in need of replacement. However, these current on-cell battery charge indicators are single use (i.e., attached to a single battery cell) and cumbersome (because typically two contact buttons must be simultaneously depressed to activate the indicator). Additionally, these on-cell battery indicators require removal of the battery from an electronic device (or package) in order to use the indicator.